Adesina maintained that the APC would not give an automatic ticket to Buhari, describing it as undemocratic.
He said Buhari has not indicated interest in seeking reelection.
Speaking in an interview on The Osasu Show, hosted by Osasu Igbinedion, Adesina noted that the party would not give an automatic ticket to any candidate.
When asked if Buhari is strong enough to handle the rigours of campaign should he decide to contest, Adesina said president’s health is a miracle and phenomenal.
He said: "As the local saying goes, you don’t shave a man's head in his absence and nobody can decide for the president. He is the one who can decide for himself.
"People can voice their opinion which they have done, people can indicate their desire but the ultimate decision will be that of the president.
"So far, we don’t have a candidate for 2019.
"In democracy, you don’t really talk of automatic ticket. In a true democracy, contest for any position should be open but there is no indication now that the president is going to throw his heart into the ring.
"The president’s health is a miracle. You marvel and give glory to God when you see him, because the comeback is phenomenal. I believe that is one of the greatest comebacks in history."
The Presidential spokesman also dismissed the insinuations that the corruption cases levelled against the Buhari administration affect the party’s victory in 2019,
He the President's integrity is not in doubt, adding that Buhari is "a man who reeks integrity."
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He also urged Nigerians to have confidence in the APC's ability to deliver the change it promised.
Adesina added, "If integrity is ever genuine, then you cant call it a smoked screen. With President Muhammadu Buhari, there was never a smoke screen.
"If I can quote scripture, there is that part that says cast away not your confidence, which has great recompense of reward. When you maintain your confidence in something good, eventually you get rewarded.
"So, I will just tell Nigerians that the confidence you had in this government of change, the confidence you had in APC that made you vote for change in 2015, keep that confidence because there is a lot that the party and this government can still do for this country. It is work in process and this work should continue.
"The man on the street has to make up his mind. It is a voluntary thing but he has to decide whether he wants to go back to bondage as signified by a government that held us in bondage for over 16 years and threatened to keep us there for 60 years.
"He has to decide whether he wants to go back into servitude and bondage or he wants to stay in liberty where he can see the promise land ahead."
He expressed pity for the Peoples Democratic Party, which he said is still reeling from the shock of losing power to the APC.